The following Patent Document 1 discloses a method for processing a base body to be processed. The method disclosed in Patent Document 1 relates to a method for manufacturing an MOS transistor. The method disclosed in Patent document 1 includes (a) patterning a silicon oxide film and a polysilicon film which are formed on a semiconductor substrate to form a gate electrode, (b) implanting ion onto the semiconductor substrate using the gate electrode as a mask to form a lightly diffused region, (c) sequentially forming a first side wall spacer layer and a second side wall spacer layer on a side wall of the gate electrode, (d) implanting ion onto the semiconductor substrate using the side wall spacer layers as masks to form a highly diffused region, and (e) forming a nickel silicide layer in the gate electrode and the highly diffused region.
In the method for manufacturing an MOS transistor, the first side wall spacer layer may be formed of silicon oxide and the second side wall spacer layer may be formed of silicon nitride in some cases. Further, after forming the nickel silicide layer, the second side wall spacer layer may be removed by dry etching. In order to dry-etch the second side wall spacer layer, generally, mixture gas containing gas (CF based gas) which includes carbon and fluorine and oxygen gas is used.